Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of the potentially enormous expense of well completion, added emphasis has been placed on well monitoring and maintenance throughout the life of the well. That is, placing added emphasis on increasing the life and productivity of a given well may help ensure that the well provides a healthy return on the significant investment involved in its completion. Thus, over the years, post-completion well diagnostics and treatment have become more sophisticated and critical facets of managing well operations.
Certain well maintenance applications involve the introduction of downhole equipment such as water jet devices, scale removal assemblies, packer placement equipment or any number of directly interventional implements. These may be delivered by pipe, coiled tubing, tractoring or other delivery systems and often involve closing off the well bore and ceasing production during the intervention. When accounting for the rig up and down time, application time, lost production, equipment and other costs, the expense of running such applications may exceed tens to hundreds of thousands of dollars.
In light of the expenses associated with direct interventions, where the opportunity arises, added emphasis has understandably been placed on well management techniques that are much less invasive. Completions assemblies in particular are often employed that include zonal isolation and flow control features that allow for modifying production over time in line with changing well conditions. So, for example, where one zone of the well becomes unproductive, say through the emergence of water, built in flow control sleeves or valves of the completions assembly may be utilized to close off fluid uptake from the zone. Thus, neighboring productive zones may be unaffected by the noted water production without the requirement of a post-completion intervention for the placement of plugs, packers or the like.
In order to actuate the noted flow control features of sliding sleeves or valves, the completions assembly is generally outfitted with a control line running from equipment at the oilfield surface. So, for example, the assembly may include tubing segments fitted to one another at a joint, each segment having a packer near the joint which accommodates the control line. Ultimately, with the assembly in place in the well, a relatively central located conduit of tubing is provided for hydrocarbon production. The internal conduit is left free of control line by utilizing packers about the tubing which include passages to accommodate the line and allow it to externally reach flow control features of the tubing segments.
In order to allow the control line to reach flow control features of the tubing from a location external to the tubing, the completions assembly may be of an eccentric configuration. That is, the tubing segments may be positioned slightly off of dead center relative the wellbore. This may be achieved by utilizing packers that, in a cross-sectional sense, have one side that is slightly fatter or wider than its opposite side. In this manner, the slightly wider side of the packers may have the space to be equipped with channels to accommodate the control line therethrough.
Aligning successive eccentric devices, such as the noted packers, may be particularly challenging. That is, with each packer affixed to a different tubing segment, proper alignment of say the wide sides of the packers at precisely the same stacked positioning about the joined tubings is dependent upon how the tubings are mated at the joint. For example, where the tubing segments are threadably joined, the alignment of the packers relative one another is dependent upon where they are positioned once the segments are fully threaded together. Of course, during design and manufacture of the packer equipped segments, they may be configured such that a completed coupling therebetween results in eccentric packers of roughly the same alignment or orientation.
Unfortunately, the degree of precision available in configuring tubing segments for oriented alignment of adjacent eccentric packers at either side of the coupling joint is less than desirable. This is not so much a matter of faulty precision as it is the severe space limitations afforded the completions assembly. For example, even with perfect alignment and the eccentric packers in an undeployed state, the amount of clearance between the assembly and the casing of the well is very minimal. Generally, this clearance is well under an inch. Thus, in circumstances where the packers are relatively close to one another, say less than about 10 feet or so, a misalignment of no more than a few degrees between the packers may result in an inability to advance the assembly within the well. That is, such a misalignment may eliminate the clearance altogether due to a lack of slack in the tubing, for example, were the packers to be separated by a greater distance.
Compounding the problem is the fact that such misalignment is often too small to be visibly detected and, even if apparent, the option of threadably loosening the joint for more proper orientation of the packers would be impractical and inadvisable. As such, operators are all too often left with the prospect of advancing the production assembly into the well in a relatively blind fashion, unsure of the prospect of the assembly reaching its targeted location, particularly without torque induced damage to the line.